Liquefied petroleum gas (LPG) is widely used as a source of energy for heating and other uses. Many thousands of homes are heated by LPG. At these homes, the gas is stored on-site in a pressurized tank which contains the liquefied material and its vapor. A pressure regulator is used to decrease and control pressure at a value which is suitable for home piping systems or other uses.
It is very important in the interest of general safety to determine if leaks exist in piping systems carrying such gases, since the range of explosive concentrations in air for such gases extends to low concentrations. One important method for detecting leaks in pipes carrying hydrocarbon gases is the addition of odorant to the gas. Since such odorant can be detected by a person at very low concentrations, odorant is helpful for detecting leaks inside closed structures, but odorant alone does not provide sufficient detection for all leaks.
Another important class of methods for detecting leaks in pipes carrying hydrocarbon gases and other gases is detection of a pressure decline when the system is closed. Testing for leaks in piping systems using pressure decline is a routine procedure. There are several methods within the LPG industry for making leak tests on piping systems. The National Fire Protection Association (NFPA) in their pamphlet No. 54 endorses the following method for checking leakage in piping systems:
"APPENDIX D: SUGGESTED METHOD FOR CHECKING FOR LEAKAGE PA1 "b. Checking for Leakage Not Using a Meter. This can be done in two ways: PA1 "(1) by attaching to an appliance orifice a manometer or equivalent device calibrated so that it can be read in increments of not more than 2 percent of operating system pressure, and momentarily turning on the gas supply and observing the gaging device for pressure drop with the gas supply shut off. No discernible drop in pressure shall occur during a period of 3 minutes; or PA1 "(2) by inserting a pressure gage between the container gas shutoff valve and the first regulator in the system, admitting full container pressure to the system and then closing the container shutoff valve. An appliance valve shall then be opened momentarily, dropping the pressure in the system between the first regulator and the container shutoff valve 10 psi. The system shall then be allowed to stand for 10 minutes without showing an increase or a decrease in the pressure gage reading."
This method necessitates the removal of piping segments, plugs or caps and the use of delicate instruments which must be calibrated and carried in shock-resistant containers.
U.S. Pat. Nos. 4,984,448 and 4,918,968 address leak detection in LPG gas systems. These methods both require partial disassembly of the system for insertion and removal of apparatus used in detecting a leak. U.S. Pat. No. 4,766,762 addresses the problem of insertion of apparatus into the piping system by permanently affixing a leak detector on the regulator. However, this method requires the full replacement of the regulator with the new regulator leak detector combination, which is costly. Pressure gages, which can be used to detect leaks in any pressurized system, are relatively expensive and difficult to use in low pressure systems.
There is a long-felt need for apparatus and method to perform a leak test in low pressure gas systems, particularly LPG systems, at the pressure regulator of the system, which does not require going inside a home or other site where the gas is being used, which would require no disassembly of the piping circuit, which operates on all existing hardware without retro-fitting any device, and which is inexpensive and easy to use.